shmem_rename() bugs (was Re: 6.19 tmpfs __d_lookup() lockup)

[Al Viro]

On Sat, Dec 13, 2025 at 07:22:41AM +0000, Al Viro wrote:

> 	What I'm going to do is a couple of patches - one fixing
> the regression in this cycle (pretty much what you'd been testing),
> then a separate fix for stable offsets failure handling (present
> since 2023).  I'll feed them to Linus; I hoped to do that with
> old regression fixed first, to reduce the PITA for backports,
> but if I don't have that debugged tomorrow, I'll send the recent
> regression fix first.

OK, I think I've got it; see

git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs.git #fixes

individual patches in followups; the first one deals with this cycle
regression, the second - with older bug in shmem_rename() failure
exits.

Folks, please review.  If nobody objects, I'll send a pull request on
Monday.